Fluoropolymers, both partially and fully fluorinated, are important articles of commerce, being especially useful as thermoplastics and elastomers. Many of these polymers exhibit excellent chemical and/or thermal stability. One of the most important classes of these polymers are those that are made by the free radical (co)polymerization of one or more fluorine containing olefins, optionally with other copolymerizable vinyl monomers and/or ethylene.
During such polymerizations, end groups on the polymers are formed, some of which may have detrimetnal effects on the polymer properties. So-called ionic end groups have such an effect. Such groups, which are themselves ionic or may easily form ions when reacted with basic compounds, may be thermally unstable and/or cause the polymer to exhibit inferior processing characteristics. For instance such end groups may significantly raise the melt viscosity of such polymers, making them more difficult to mix and shape and/or cause instability in the polymer.
The end groups found on such polymers are often fragments of molecules that were part of the free radical initiator (system) or decomposition products thereof, and if present, any chain transfer agents. Therefore the nature of the initiator affects the nature of the polymer end groups.
U.S. Pat. No. 5,285,002 describes the polymerization of fluorine containing olefins using a fluoroaliphatic sulfinate and an oxidizing agent as a source of free radicals. No mention is made of the use of bromates, chlorates or hypochlorites as oxidizing agents.